I. Field of the Invention
The invention relates to a method of repairing large fixed passageways. In particular it is directed to the use of fiberglass sandwiches as a liner to effect the repair of concrete sewage and chemical pipes or tunnels which cannot be rotated.
II. Background of the Invention
Large diameter sewage and chemical pipes (at least 48 inch) are formed by utilizing cast concrete. The pipes are buried and have a life expectancy of up to eighty years. When such pipes develop leaks it is expensive to either replace or repair them.
Since these pipes are originally constructed from concrete, those of ordinary skill in the art have looked to conventional concrete techniques for means of repairing these concrete pipes. The traditional means of repairing large diameter sewage and chemical pipes is to apply a wire mesh to the interior surfaces and spray same with gunite. A limitation on this technique is that the repairs last only three to five years.
The use of fiberglass laminates has achieved substantial acceptance in a number of fields. The laminates may be used in sandwich composite construction using a lightweight core material. It is generally believed in the industry that it is not feasible to apply these laminates and/or composites in overhead applications. This applies to the repair of underground or other fixed pipes where the pipes cannot be rotated to allow conventional application of the laminates.
An object of the present invention is to provide a means of reconstructing large diameter underground pipes and ducts, thereby increasing the life of the pipe significantly. A second object of the invention is to provide a means of reconstructing large diameter underground pipes and ducts without seriously affecting the pipe and duct capacity. A third object of the invention is to provide an economical and efficient means of reconstructing large diameter passageways. A final object of the invention is to provide a means of applying a fiberglass sandwich to the overhead surface of an underground passageway, where rotation of the passageway is impossible.